578 THE ANIMAL PARASITES OF MAN 



and broad, of four segments, bent ; wings broad and in some iridescent, legs stout. 

 The male has holoptic eyes, whilst in the female they are small and widely separate. 

 The sucking proboscis is short. The thorax and abdomen are clothed with short 

 hairs which may form spots and markings ; these are golden, silvery, grey, or brown- 

 ish. In the sub-genus Pro-Simulium the second segment of the hind tarsi in both 

 sexes is elongate, linear, and without a basal notch ; in Eu-Simulium it is short, 

 curved, and dorsally notched at the base. 



Simulidce often occur in swarms, and attack not only man but cattle, horses, 

 and poultry. In some districts they are more annoying than mosquitoes. 



Their life-cycle has been most completely worked out by King, in Africa. 



The larvae and pupae occur in swiftly flowing water, by waterfalls, in rapids, etc. 

 The ova are laid in gelatinous masses on plants or rocks close to or overhanging the 

 water. The larva is cylindrical, enlarged posteriorly, where it is provided with a 

 sucker, by means of which it attaches itself to a rock, water weeds, debris, etc. ; 

 anteriorly it has a proleg close behind the head on the lower surface. The head is 

 dark and chitinous. The respiration takes place by means of branched tracheal gills 

 which protrude from the dorsal surface of the last body segment ; they are retractile. 

 The colour varies from deep green to yellow or almost black. Their food consists of 

 algae and other organisms in the water brought to their mouth by two fan-like organs 

 .placed on the head. The larvae can crawl from place to place by means of the 

 thoracic proleg ; they occur in masses, usually in a more or less erect attitude. A net- 

 work of threads is spun on their support, by means of which King tell us " they are 

 enabled to maintain their position against the strongest current ; frequently they will 

 leave their support and let themselves out into the stream anchored by threads of 

 silk and enabled by them to return." 



When full fed the larva spins a pocket-shaped cocoon on the support, within 

 which it pupates. The pupa is motionless and has a pair of branched spiracles pro- 

 jecting from behind the head. When the adult emerges, a bubble of air collects 

 around it, and in this it floats to the surface and at once takes wing. The European 

 species take a month to complete larval life, a week being spent in the pupal stage. 

 The flies are most restless, and even when stationary continually move their legs 

 about like feelers. Sometimes the swarms consist entirely of females, sometimes 

 early in the season mostly of males. 



The females pierce the skin of humans on tender spots, such as ears, the fore- 

 head, around the eyes and nose, and crawl into the cavities. They are quite harmless 

 at night, mainly attacking about sunrise and sunset. Some crawl up the arms and 

 legs and down the neck, and leave behind little red weals which itch intensely 

 (S. damnosum, Theob.), and blood may flow freely from the wounds. 



The following are some of the worst species : 



SimuUum columbaschensis, the " Kolumbatz fly," which abounds in the damp 

 marshy lands along the Danube, and is a great plague to man and beasts in Hungary, 

 and is also abundant in Austria and Moravia, and is most numerous after inunda- 

 tions from the Danube. They sometimes appear in such swarms that it is impossible 

 to breathe without getting them into one's month. There are instances of children 

 being killed by these flies when left on the ground by their mothers when working 

 in the fields. 



S. damnosuni) Theob. This occurs throughout Equatorial Africa and is known 

 as the "jinja fly" in Uganda, the "fouron" in the French Congo, the "kilteb" 

 in the Sudan. It is a most vicious biter, and in some parts occurs in "belts"; 

 Dr. Christy found one such extending from the shores of the Victoria Nyanza 

 rthwards along the right bank of the Nile for twelve or fifteen miles or more, and 

 perhaps three or four miles wide. In this area the flies swarm in millions at certain 



